A school uniform shirt for girls has been found to contain a substance which can cause cancer, says a new investigative report.

The report, which was conducted by the Consumer Council, tested 49 uniforms from 22 different suppliers. The uniforms were tested for their durability after washing, the pH (the scale of how acidic something is) of the material, and the presence of toxic substances such as fluorescent brighteners and formaldehyde.

While none of the uniforms contained dangerous amounts of formaldehyde, a dye which contains another harmful chemical was found to have been used in girls’ school uniforms. The amount found was 173mg/kg, at least eight times higher than the safety threshold of 20 mg/kg.

Parts of the uniforms, which were sold by uniform shop Shing Shun Fat in North Point, were dyed with azo dyes. These dyes can release a chemical which may have health risks and carcinogenic side-effects if they are in direct contact with the skin. Additionally, fabric of uniforms for male students from the same store were found to have high pH levels, which can cause skin irritation.

White trousers from the store had a pH level of 8.7, above the safety threshold of 8.5. The report said that the pH level goes back down to normal after washing the trousers once.

Customs officials seized 17 uniforms from the shop in question this morning; the shop supplies schools such as Kiangsu-Chekiang College with their uniforms.